Ansprechpartner

Behavioural Biology . Cognitive Science

Pointers for evolutionary biologists

This relativizes the hitherto accepted belief that the theory of mind is an exclusively human ability. But how much do apes actually understand about the state of knowledge of others? Is it possible that they are able to use pointing gestures or other referential indications in communicative contexts? “These questions are extremely fascinating for us,” says biologist Juliane Bräuer, who researches the social cognition in various animal species in Tomasello’s department. “The comparison between the different species provides us with insight into ourselves and what has changed in the course of our development. After all, how human cognition developed during the course of evolution is one of our big questions.”

Humans are thus endowed with the ability to put themselves in the perception and action perspectives of others, and this ability plays a major role in early childhood language acquisition. The child learns the names of objects from the mother or father by pointing to them. It is now also assumed that gestures actually lie at the root of language: the sounds and words only followed after the pointing.

However, as Call and his colleagues discovered to their amazement while researching at the Wolfgang Köhler Primate Research Center, the great apes did not follow even the broadest of hints: a series of studies with hidden pieces of fruit showed that pointing does not work in human-ape communication – the apes clearly do not understand what their human test partners want to tell them when they point to a certain container. Based on these findings, it appeared that the ability to interpret communicative gestures is a talent exclusive to Homo sapiens. If man’s closest relation in ontogenetic terms cannot understand pointing gestures, who can? The answer came from an unexpected source: “My dog can do it!” claimed then doctoral student Brian Hare (MAXPLANCKRESEARCH 2/2006, page 70 ff.).

With this off-hand comment, Hare landed himself a commission to carry out his own research project. It quickly emerged that his dog was not the only extraordinarily gifted canine communicator that was able to interpret human pointing gestures. As had been done in the ape house, the “object-choice test” was used here, too. The dogs were presented with two identical upturned containers, only one of which contained a dog biscuit. The dogs could not have known which container concealed the biscuit as they had not seen it being hidden.

Their human test partner then pointed to the container with the interesting content. After this, the dogs were allowed to choose, and did so, by touching the container of their choice with their noses or paws. If they chose the correct one, they were rewarded with the contents; if they chose the wrong one, they were left empty-handed. To ensure that the dogs were not being led by their sensitive noses, a control condition was carried out in which there were no referential clues to the correct container. “If the animal made alternately correct and incorrect selections in this case, it was clear that it was not able to smell the food,” says Juliane Bräuer, explaining how Hare’s claim was put to the test.

This study alone revealed that Brian Hare’s claim was no empty promise. The dogs showed a clear preference for the container to which the human had pointed: the unspoken message had clearly been heard. “Hare’s article about dog cognition was published in 1998,” explains the 33-year-old biologist. She herself has been working at the Max Planck Institute since 1999 and wrote her graduate diploma thesis there in 2002. Around the same time, a group of researchers in Budapest were exploring the question as to how human gestures can be of use to dogs.